(A) Field of the Invention
The present invention relates to multi-parameter inspection systems, and more particularly, to a method for enhancing the measurement capability of multi-parameter inspection systems.
(B) Description of the Related Art
Multi-parameter inspection systems such as spectrometers, ellipsometers and scatterometers are very important inspection devices, and are widely used in several fields such as the semiconductor industry, the thin film optics and the optical communication industry.
Multi-parameter inspection systems, which measure more than one parameter simultaneously, analyze a set of measured signals to obtain values of each parameter at the same time. Practically, however, these parameters are not independent, therefore there is likely to be an incorrect measurement in the results due to a correlation between parameters. If such correlation exists, it will not only affect the accuracy of the obtained value but will reduce the precision of the inspection system as well.
“Spectroscopic ellipsometry-based scatterometry for depth and line width measurements of polysilicon-filled deep trenches” by Thomas Hingst, et al. (Metrology, Inspection, and Process Control for Microlithography XVIII, edited by Richard M. Silver, Proceedings of SPIE Vol. 5375, 2004) reported that how to avoid parameter correlation is a very important issue.
Also, “A Comprehensive Test of Optical Scatterometry Readiness for 65 nm Technology Production” by Vladimir A. Ukraintsev (Metrology, Inspection, and Process Control for Microlithography XX, edited by Chas N. Archie, Proc. of SPIE Vol. 6152,61521G, 2006) reported that a solution to the problem of parameter correlation would be of great value.
However, these two papers did not provide a proper solution to the problem of parameter correlation. In short, as the related manufacturing process technology has developed, the standard of the accuracy and precision of inspection systems has become higher, so it has become more important to solve the long existing but often neglected problem of parameter correlation.